. Issued February 28, 1923 Washington, D. C. Vv | Revised May, 1929

THE FREEZING TEMPERATURES OF SOME FRUITS, VEGETABLES, AND CUT FLOWERS

By R. C. Wricut, Physiologist, and Grorer F. Taytor, formerly Biophysicist, Office of Horticultural Crops and Diseases, Bureau of Plant Industry

INTRODUCTION

There is an ever-increasing demand from persons interested in the growing, shipping, and handling of produce for exact data on the freezing points, or the temperatures at which various products freeze.

The extent of damage due to the freezing of produce in transit naturally varies from year to year, but it is usually very heavy, ageregating frequently several hundreds of thousands of dollars— during a year. ‘This in general applies not only to such products as apples and potatoes, most of which are grown in the North and har- vested and shipped in the late fall and winter, but to products which are grown in the South and Southwest during the winter and shipped to the northern markets. This latter group includes citrus fruits, strawberries, tomatoes, lettuce, string beans, cabbage, cauliflower, egeplant, etc. Cars of these food products often leave the shipping point under refrigeration and in 24 to 36 hours may pass into a zone of freezing temperatures. As they approach the more northern markets they may be exposed to temperatures ranging several degrees below their freezing point. Under certain conditions when harvested in warm weather some of these products are precooled—that is, rapidly cooled to a refrigerating temperature, either immediately before or directly after they are placed in the car for shipment, in order to delay maturity and consequent deterioration. Where precooling is practiced, itis, of course, essential to know the temperatures to which the prod- uct can be lowered with absolute safety.

It is of great importance to the commercial cold-storage man to know the exact freezing points of fruits and vegetables that he handles. In most cases fruits and vegetables other than dried or prepared products when placed in cold storage are alive, and the problem is to keep them alive and healthy throughout their storage period. Since various fruits and vegetables freeze at different temperatures, there is more or less doubt in the minds of those inter- ested as to the proper and safe temperatures at which to hold these various products in storage. One of the problems in the storage of many of these products is to hold them at a temperature low enough to slow down the living processes in order to prolong their storage life

41676°—29

2 BULLETIN 1133, U. S. DEPARTMENT OF AGRICULTURE

and yet not allow them to be damaged by actual freezing. With

many products this storage temperature is only 1 or 2 degrees above the actual freezing point. Of course some products, such as berries, may be purposely kept in a frozen condition below freezing temperature, but this subject comes under the head of freezing storage and will not be discussed here. It is therefore essential in commercial work of this kind that accurate data be at hand on the temperatures to which these products can be exposed without injuring their keeping qualities or market value.

It should be borne in mind, however, that freezing or freezing injury does not always occur when fruit or vegetable products are exposed to temperatures at or below their true freezing points. This is shown in the studies on potatoes reported in a previous publication, where tubers were cooled as much as 10° F. below their freezing points without actually having become frozen and again warmed up without apparent injury. The commonly known fact that some kinds of products may be actually irozen and then thawed out under certain conditions with no apparent injurious effects constitutes further evidence on this point. On the other hand, certain commodities such as tomatoes, bananas, and cucumbers are injured if stored at temperatures many degrees above their actual freezing points. This is usually termed chilling injury. It is evident, therefore, that tem- peratures just above the freezing point can not be regarded as safe for all types or varieties of fruits and vegetables. It is also noticeable that there are some variations in the freezing points of fruits or vege- tables of the same variety and from the same lot, as is shown in the tables that follow. Furthermore, it is quite probable that different individuals of the same variety and strain when grown under different conditions will have somewhat different average freezing points. Attention is therefore called to the fact that the freezing points given in the following tables should be considered as danger points; that is, at or near these temperatures, either above or below them, there is a possibility that the product will be in danger of injury by freezing if exposed for a sufficient length of time. These are temperatures at which it is unsafe to hold produce which is to be used for food if it is desired to maintain it for any length of time in a living condition.

The determinations of the freezing points of a number of fruits and vegetables have been made by the Bureau of Plant Industry in connection with its cold-storage investigations. By freezing point is meant the temperature at which ice crystals begin to form within the product, either fruit or vegetable.

Some 10,000 of these determinations have already been made on many varieties of commercially grown fruits and vegetables, and work is bemg continued. Jt has been found in some cases that the freezing points of some varieties are liable to slight variations from year to year, even though the same strain grown in the same locality is used. These variations, however, are probably of more importance in the study of the exact causes and results of freezing injury than from the point of view of the commercial cold-storage and produce man, for the variation of a fraction of a degree hardly warrants any change in the treatment of the product. It therefore seems advisable to publish the results of these investigations from

1 WRIGHT, R. C., AND TAYLOR, GEORGE F. FREEZING INJURY TO POTATOES WHEN UNDERCOOLED, U. S. Dept. Agr. Bul. 916, 15 p., 1 fig., 1 pL 1921. Literature cited, p. 15. as e?7se.? . ee e

FREEZING TEMPERATURES OF FRUITS, ETC. 3

time to time as obtained, because of the need for such information

and because there is no comprehensive publication on the subject. | The method of determining freezing points has been described in

former papers,” and a repetition of this description is not required here.

FREEZING POINTS OF FRUITS

Where several varieties of one kind of fruit were investigated the results are given separately to allow comparisons to be made.

Apples.—Freezing-point determinations were made for a number of authentic varieties of summer or early apples and of fall and winter varieties, most of which were grown on the Arlington Experi- ment Farm, Rosslyn, Va. The tabulated results given by varieties are shown in Table 1. These results show considerable varietal dif- ferences among both summer and winter apples. The average of all summer varieties is practically the same as that of winter varieties, the former being 28.44° while the latter is 28.51° F. These results show very little difference between the freezing points of eastern- grown and western-grown fruit.

Cherries —Freezing-point determinations were made for seven varieties of cherries grown on the Arlington Experiment Farm. The average of all varieties was 27.81° F. (Table 1.)

Grapes.—Results were obtained from the freezing of seven American and two European varieties of grapes. The average freezing point of the American varieties was 28.16° F., and that of the European varieties was 24.60°. (Table 1.)

Oranges.—The average freezing point of the six varieties of oranges studied was 28.03° F. (Table 1.)

Peaches.—Freezing-point determinations were made for 11 va- rieties of peaches grown near Leesburg, Va., in the Loudoun orchard of the American Fruit Growers (Inc.). Peaches in the hard-ripe stage were utiltzed for these tests. The average freezing point of all varieties when hard ripe was found to be 29.41° F. (Table 1.)

Plums.—Freezing points were obtained for four varieties of plums that were grown in California and purchased on the market and for one variety (Red June) grown at the Arlington Experiment Farm. The variety with the lowest freezing point is Tragedy, with a freezing temperature of 27:21° F. The average freezing point of all varieties is 28.53°.- (Table 1.)

Strawberries.—Freezing-point determinations were obtained for 22 authentic varieties of strawberries grown at the Maryland Agri- cultural Experiment Station. The greatest difference was found between the Lupton, which froze at 28.84°, and the Hustler, at 30.48° F. The average for all varieties was 29.93°. (Table 1.)

2 TAYLOR, GEORGE F. SOME IMPROVEMENTS ON THE NEEDLE TYPE THERMOCOUPLE FOR LOW-TEMPERA- TURE WORK. Jour. Ind. and Eng. Chem., v. 12, p. 797-798, 1 fig. 1920.

WRIGHT, R. C.,and HARVEY, R. B. THE FREEZING POINT OF POTATOES AS DETERMINED BY THE THERMO=- ELECTRIC METHOD. U.S. Dept. Agr. Bul. 895, 7 p., 1 fig. 1921. Bibliographical footnotes.

Wriacut, R. C.,and TAYLOR, GEORGE F. FREEZING INJURY TO POTATOES WHEN UNDERCOOLED. U.S; Dept. Agr, Bul, 916, 15 p,, | fig., 1 pl, 1921, Literature cited, p, 15,

BULLETIN 1133, U. S. DEPARTMENT OF AGRICULTURE

TABLE 1.—Average and extreme freezing points of fruits

Fruit and varieties

Apples, summer varieties:| Yellow Transparent__ Red Astrachan___-___ Marly Ripe: 222222 bs Red Jungs = 2 82 22

Marlyioe ses te

Average (not in- cluding the crab apple) 22--- 222852

Apples, fall and winter varieties, eastern grown:| Baldwin Sil ues A fery Gime

Stayman Winesap____| RWunesapes: cele. 2e Yellow Newtown_-_-_-_ York Imperial_______-

PAVGRAG Os sue eres 2

Apples, fall and winter | Varieties, western grown: Delicious DE BE Re

Rome Beauty____---- Esopus (Spitzenberg) Winesap-_______--_---

Cherries: Early Richmond__-__- Montmorency--_-_-_-___- St. Medard-__-_._____- Royal N ouville_______

INMGCReE ee aed, | Bigarreau (unknown Var lety)-

HAV ORALO ses oe et 2 2 22]

Grapes: American varieties— New Concord- eee

Dracut Amber --_- Moores Early _-__- Captivator______- Campbell (black) | Mericadel_______-

Average________

European varieties— Mialagan 2557622

Florida Seedling_____-_| Washington Navel _-_-_|

Temperatures (° F.)

| Oranges—Continued.

Extremes

Aver- age | Mini- | Maxi-

mum mum 27.72. | 27.29 28. 16 28.58 | 28. 25 28.7 29.18 | 28.82 29. 47 29.59 | 29.29 29. 71 |) 27.38 | 27.32 27. 41 | 28.46 | 27.93 28. 03 98.83 | 28.49 29. 00 | 27.81 | 27.60 28. 49 26.70 | 26.62 26. 76 28.44 | 28.12] 28.62 || 29.04 | 28.84 29. 43 98. GIs QR a 28. 96 28.48 | 28.16 29. 10 | 28.97 | 28.82 29. 05 |! 28.22 | 27.79 28. 69 || 28.50 | 28.45 28. 55 28.55 | 28. 34 28. 90 28.51 | 28.02 28. 91 28.23 | 27.93 28. 72 28.00 | 27.80 28. 20 28.34 | 28.10 28. 50 28.49 | 28.22 28, 82 28.36 | 27.98 28. 86 98.55 | 28. 26 29. 05 28.60 | 28. 26 29. 05 28.35 | 28.02 28. 7 28.92 | 28.72 29. 38 28.69 | 28. 26 29. 05 28.24 | 27.93 28, 35 28.53 | 28.20 28. 92 27.94 | 27.60 28. 35 28.10 | 27.79 28. 58 28.09 | 27.60 28. 58 28.16 | 27.95 28. 50 27.65 | 27.37 28, 21 26.88 | 26.76 27. 69 FH SSE RS 27. 83 27.81 | 27.56 28. 25 28.39 | 27.93 28. 68 28. 21 7. 83 28. 63 TRS 2777 28. 10 28.28 | 28.15 28. 62 27.86 | 27.14 28. 05 27.96 | 27.77 28. 00 28.54 | 28.40 28. 54 28.16 | 27.85 28. 37 24.60 | 24.60 24. 80 24.60 | 24.10 24. 76 24.60 | 24. 35 24. 78 28.64 | 28.34 28, 82 || 27.72 | 27.60 27. 83 28.20 | 28.10 28, 43 28.42 | 28.

Fruit and varieties

Valencia (California) - Satsuma (Owari va- Riehy)f7.ek ee

AV CLALC ne Seen Benes (hard ripe):

Tragedy Disha a I cen

Excelsior’. ee | Barly Ozarks se8 Early Jersey Giant___ Gandy se) see ee Gien?Mary2 she Howard 17 (Premier) Frastler==2sSe=o=— =

Kellog (Kellog’s Pride)

Lupton _._ =3=- = 5.4

Crystal White________ Logan (Loganberry) _

' Raspberries:

ee (St. ic

Columbia (black) -__- Cranberries:

Searl - or Mare ee

Gebhart Beauty______

Mammoth Rey ahaa ee

Perry: Rede ee Barkly: Black: =... 3222

IHOWeS: 2. eee Pride 9 eae

Temperatures (° F.)

MIKERSISSSESR

Extremes Aver- age | Mini- | Maxi- mum mum 27.01 | 26.90 | 27.60 25.18 | 27.93! 28.68 28.03 | 27.86 | 28.34 29.82 | 29.50 | 30. 29.72 | 29.43| 30. 28.65 | 28.25 | 28. 29.40} 29.30| 29. 29.56 | 29.10| 30. 98.90} 28.35| 28. 29.28 | 29.05| 29. 29.57 | 29.10| 29. 30.02 | 29.90] 30. 29.57 | 29.30] 29. 29.06 | 28.73| 29. 29.41} 29.09| 29. 29.26 | 29.05} 29.80 29.53 | 29.19] 29.75 27.21 | -26.76 | 27.41 98:13 | 27.79| 28.44 28. 53 28. 85 29. 70 29.75 30. 03 30. 05 29. 98 30. 19 29, 96 30. 36 30. 29 30. 32 29. 82 29, 99 29. 94 30. 04 29. 82 30. 13 29, 82 30. 22 29. 24 29. 55 30. 08 30. 16 30. 23 30. 38 30. 48 30. 60 29. 59 29. 90 30. 13 30. 48 30. 25 30. 26 28. 29. 10 30. 05 30. 13 30. 18 30. 42 30. 38 30. 48 30. 46 30. 81 29, 22 29. 53 29. 93 30. 13 29. 09 29. 30 29. 21 29. 54 28. 40 28. 63 29, 51 29.75 30. 41 30. 50 28. 76 28. 79 28. 20 28. 44 26. 30 26. 60 26. 70 | 26. 90 25. 60 25. 80 26. 89 97. 36 97. 93 28. 05 28. 10 98.71 29. 02 29. 45 25. 03 25. 74 28. 24 28. 43 27. 05 97.73 28. 00

FREEZING TEMPERATURES OF FRUITS, ETC. 9)

Tas 1.—Average and extreme freezing points of fruits—Continued

SUMMARY OF AVERAGES

Temperatures (° F.) Temperatures (° F.)

». Fruit and varieties eer BERNE AS Fruit and varieties eor Txtremaes age age vie : Mini- | Maxi- Mini- | Maxi- mum | mum mum | mum Apples: Grape init 22 ee od 28.36 | 28.00 28. 50 Summer varieties__--| 28.44 | 28.12 QRAG2 it) LECMONS ss As eMe le NeW 28.14 | 27.89 28. 47 Fall and winter ------ 28.51 | 28.21 D887 Win OLraMgestee. Menlen Sae ho 28.03 | 27.86 28. 34 Bananas (Jamaica): Peaches (hard ripe) -__--- 29.41 | 29.09 29. 74 Baya Peele sxc 22 29.84 | 29.76 29.92 || Pears (Bartlett): ESET 30.22 | 30.10} 30.58 Hard nipes aus 28.46 | 28.06 | 28.70 Ri ante Ley pais 22 Pe2ON Gules oalo 29. 53 Soft ripe ye ee ae 27.83 | 27.20 28. 00 OSs Typo we Sees 26.00 | 25. 45 26.50 || Pears (unknown Japa- ‘ Blackberries: nese variety) _________-- 29.39 | 29.34 29. 53 Black varieties_______ 29.15 | 28.73 29.42 || Japanese persimmons White varieties______- 28.40 | 28.12 28. 63 (Tanenashi)___.____-__- 28.33 | 28.07 28. 63 Logan (Loganberry)_| 29.51 | 29.32 HS) (A) |i AE lbbbosyu ee 28.53 | 28. 20 28. 85 @HErniGs ee Aee NT NR 27.81 | 27.56 28. 25 || Raspberries: @ranberriesssyio2 ways sis 27.16 | 26. 28 26. 93 Red varieties________- 30.41 | 30.12 30. 50 @urrants ee Le Na 30221) | BON18i | 80525 Black varieties______- 28.76 | 28. 24 28. 79 Gooseberries _____________ 28. 91 28. 70 29.18 || Strawberries____________- 29. 93 29. 56 30. 13 Grapes: Chestnuts (Italian) ______ 23.80 | 23.00 24, 20 Ameri¢an 2). 2). 28.16 | 27.85 28.37 || Walnuts (Persian or so- Huropeansse. 2 82 = 24.60 | 24.35 24. 78 called English)_._--___- 20.00 | 19.80 22.10

Blackberries, raspberries, and cranberries.—Three varieties of black- berries were frozen, viz, Jumbo, Eldorado, and Crystal White. The two black varieties froze at 29.09° and 29.21° F., respectively, - while the white variety froze at 28.40°. Logan blackberries (eastern grown), froze at 29.51°. One variety each of red and black rasp- berries was frozen. The Ranere (St. Regis) froze at 30.41°, while the Columbia froze at 28.76°. Four varieties of cranberries grown in Wisconsin and eight varieties grown in Massachusetts were frozen. Considerable differences were found in the freezing points of some of these varieties. While the McFarlin variety froze at 29.02°, Shaw’s Success froze at 25.03°. The results for Gebhart Beauty and Mam- moth are intermediate, being 26.30° and 26.70°, respectively.

Miscellaneous fruits—A number of other fruits and berries were investigated, but only one variety was available in each case. The results are therefore not given separately, but are included in the summary of Table 1 covering the average freezing points of all the fruits studied. ‘Two varieties of nuts were frozen, viz, Italian chest- nuts, which froze at 23.80° and Persian or so-called English walnuts, which froze at 20.00° F.

FREEZING POINTS OF VEGETABLES

While several different kinds of vegetables have been used in the freezing-point determinations, those on which the most extensive variety studies have been centered are potatoes, sweet potatoes, and tomatoes.

Potatoes.—Freezing-point determinations were made on 18 dif- ferent authentic varieties of potatoes. Bulletins 895 and 916 of the United States Department of Agriculture give the results of this study in detail, so they will not be discussed here. The average freezing points of all varieties was 28.92° F. (Table 2.) |

TABLE 2.—Average and extreme freezing points of

and other

Temperatures (° F.)

vegetables

BULLETIN 1133, U. S. DEPARTMENT OF AGRICULTURE

potatoes, sweet potatoes, tomatoes,

Temperatures (° F.) -

Kind and variety ere Degrees Kind and variety ieee AE ELSS age | Mini- | Maxi- | age | Mini- | Maxi- mum | mum | mum | mum Potatoes: Tomatoes (ripe)—Contd. ANNI NY eee e 29.20 | 29.00 29. 3 Stoneem ieee 30.31 | 30.10 30. 58 Early Prospect___---- 28.80 | 28. 72 29. 30 Greater Baltimore____| 30.62} 30.20 30. 81 Trish Cobbler ___.__-- 29.67 | 29.60 29. 7 Colunbia= 30. 31 30. 29 30. 77 BiTSGe anya 29.00 | 28.88 29. 00 Delaware Beauty____| 30.02 | 29.95 30. 33 First Early Standard_| 28.97 | 28.74 29. 12 Livingston’s Globe___| 30.58} 30.32 30. 88 Whnolaess02 2b ees 29.17 | 29.01 29. 30 Livingston’s Acme___| 30.46 | 30.41 30. 74 Spaulding No. 4_____- 29) 33: |) 29521 29. 32 Greenhouse varieties— Green Mountain_-_-_-_- 28.50 | 28.38 28. 55 Carter’s Sunrise__| 30.58 | 30.06 30. 85 GoldiCoine= = 28.63 | 28.40 28. 70 Stirling Castle___| 30.54 | 30.41 30. 60 Rural New Yorker_-_-_| 28.70 | 28.46 28. 75 Ere ee oe 28.32! 28.30 28. 48 AV CLA ZO ne eee 30. 38 | 30.20 30. 67 . S. Seedling No. f 8774 ae ee 28.77 | 28.65 | 28,83 || Pomatoes (green): Bonny Besta =e ee 30. 57 | 30.38 30. 83 Up-to-date Sesesoosesoe ss 29. 10 29. 10 29. 10 E li 30 24 29 q7 30 58 Producer_____.._-_.-- 28.70 | 28.'73° | 28. 79 3 FT iGeeoe! oo S0.fs | a0en | aps Oregon White Rose_-| 28.71 | 28.60 | 28.80 eae a Vann apa Ie SWenyl ak) oe British Queen_______- 29.27 | 29.22| 29.30 Red y rae eee saice | cao taeda, Garnet Chile_________ 28.16 | 28.00] 28.28 Gene ee de ane 30.15 | 30.10 | 30.38 American Giant_____- 29.64 | 29.48| 29.68 || OE aoe sees le Greenhouse varies sa ay tan oe mee arter’s Sunrise__ . ! Bex Average..--.------- 28. 92} | 28.80 | 29.02 Stirling Castle._-| 30.11 | 29.90 | 30.15 Sweet potatoes: Bie ae eras Rane ea eed 28. 05 zr. 28. 72 Average.._--.-- 30. 40 30. 21 30. 57 OOlGYa52 eee 28. 46 27. 28. 91 Early Carolina____--- 28: 59 |. 28: 40.| 228, 96 || weston: Raye | os cs | oe Gcorsian sees 28.05 | 27.79| 28.58 Gen Pa aa Be. oe ealen a 48 Gold Skin...__._____- 98.47 | 28.21| 28.63 ountry Genome Less ore Improved Big Stem__| 28.76 | 28.26] 29.00 Ey oan et ees FR 2B laa See tgiee Miles. 2S Ce 98.34! 28.16| 28.54 olden Bantam_-_--- 6 ao : INancyorlaliess = 8 28.10 | 27. 54 28. 35 i Mullihan = 0 97.64 | 27.46 | 27.93 Average------------ 28.95 | 28.65 | 29.22 Pierson: eke leis 28.68 | 28. 02 28.72 || Onions: ee IED AO ISD. ee | 28.34 | 27.87 28. 68 Yellow Danvers____-_- 30.10; 29.61 30. 17 BUMP kine eee 28. 98 28. 68 29. 09 White Globe_________ 30. 20 29. 75 30. 41 REGO Brazile ee 28.40 ; 28.30 28. 63 Texas Bermuda__-_-__- 29. 96 29. 71 30. 13 Red Bermuda_____-_- 28. 17 27. 98 28. 63 | Red Jerseys sae! aes 28.52 | 28.30 28. 77 Averages. oS 30.09 | 29. 69 | 30. 24 Southern Queen_____- 28. af zB. oa 28. 82 Tbiyeareee RIUM eee eer 28. 4 ; 28. 72 : Yellow Belmont____. 28.57 | 28.49| 28.39 Tay ree Ra Fs 300) stage [hese Yellow Jersey________ 98.97 | 28.26] 29.05 Prive Hi RETA RE 31.57 | 3L45| 3177 Yellow Strasburg____| 28.72] 28.30] 29.00 MAS TE Sas 8 22 aie : ws : Average_________._- 28, 44 28. 10 28. 72 7 aXs' (2) 621A ee mS 31. 20 31. 03 31. 38 Tomatoes (ripe): Canids Sl SS ig Bonny Best__________ 30.60 | 30.48 30. 68 Beat Nae reer ty a 29. : : Olney Special ——------ 30.59 | 30.34] 30.67 Chantenay ---------- 29,99 [2s arlama cesses ieee 30. 52 30. 43 30. 77 JohniBaer 2-2 30.57 | 30.24] 30.90 OCU BE ceca cocoa UY ee | rie Mandrethess ste ae) 30.45 | 30. 34 30. 72 || Peas: | Early Michigan______ 30.67 | 30.19 30. 85 Early Alaska________- 93 | 28. 26 29. 19 MATAV Clit ete ee oe 30.03 | 29.90 30. 38 Horsford’s Market Bloomdaleiaay i wi 29.99 | 29.90 30. 53 Gardents £3 30.93 | 30.73 30. 99 RedyRock_ aro ey 30.55 | 30.48 30. 62 Maxtonianes ¢-<s. se 30. 23 | 30.03 30. 56 Rruckersvhavonites=s| oO; 0O Neen eee Eee en ING wa Glonyaes een 29.78 | 29.63 30. 38 Asverage._i:. hiss 30.03 | 29.67 | 30.25 SUMMARY OF AVERAGES iBeansk(Snap) =see ae 29. 74 29. 65 30:063| |Huethwiees=--- cen eee 31. 20 31. 03 31. 38 Cabbage (Early Jersey Onions Gry) eon ee 30.09 | 29.69 30. 24 Wakefield)_____._______ 31.18 | 31.06 31.34 || Onion sets (Yellow Carrotstec iene an eee 29.57 | 29.42 29. 68 Globe). 732 8 ee 29.50 | 29.00 29. 90 Caulifiower._2____-_____- 30.08 | 29.95 | 30.15 || Peas (green)__-_.________- 30.03 | 29. 67 30. 25 Gelery) Va ew Las 29.73 | 29.7 30,00: || Potatoess+- /2ou.e1) eee 28.92 | 28.80 29. 02 Corn sweet 2 oa 28.95 | 28.65 29, 22 || Potatoes, sweet___-_____- 28.44 | 28.10 28. 72 Beeplant css Seem ree 30.41 | 30.17 | 30.69 || Tomatoes (ripe)_-_______- 30.38 | 30.20 30. 67 KKonirabie 2) ae eee 30. 02 29. 74 | 30/22.) Duan Ses eee Sere 30. 23 30. 16 30. 48

Sweet potatoes ——The results of freezing 20 more or less common

varieties of sweet potatoes are presented in Table 2.

The varieties

with the lowest freezing points are Big Stem and Georgia, both of

which froze at 28.05° F.

The highest freezing points were found

FREEZING TEMPERATURES OF FRUITS, ETC. 7

with Pumpkin and Yellow Jersey varieties, which froze at 28.98° and 28.97°, respectively. The average of all varieties was 28.44°.

_ Lomatoes:—The freezing temperatures of 19 commercially grown varleties of tomatoes were determined and are presented in Table 2.

These tomatoes .were all grown under the same conditions at the

Arlington Experiment Farm. Determinations were made on both —

Tipe and practically full-grown green specimens, such as are usually picked for shipment from the Southern States to the northern mar-

difference in the average freezing points of ripe and green tomatoes, the averages being 30.38° and 30.40°, respectively. |

Sweet corn.—The freezing point of sweet corn varied considerably with the age of the product. There was also considerable variation between varieties. Four varieties were studied. (See Table 25)

Miscellaneous vegetables.—The freezing points of three varieties of onions, three varicties of lettuce, two varieties of carrots, and three varieties of peas, and of at least one variety each of beans, cabbage, cauliflower, celery, eggplant, kohl-rabi, onions, and turnips are also presented in the body or in the Summary of Table 2.

; FREEZING POINTS OF CUT FLOWERS

Requests have been received for information on the freezing points of such cut flowers as are commonly held in cold storage or shipped In quantities. Determinations were made for peonies, roses, and Haster lilies, and these are presented in Table 3. Results are shown for both petals and leaves. With peonies and roses the petals freeze at temperatures higher than do the leaves. Rose petals froze at 30.04° F., while peony petals did not freeze until a temperature of 29.05° was reached. In the case of Easter lilies the leaves froze before the petals, the latter hot succumbing until the temperature reached 27.50°.

TABLE 3.—A verage freezing points of the petals and leaves of cut flowers

Peony Rose Easter lily Scope of inquiry rT) | tei Gi. Petals Leaves Petals Leaves Petals Leaves Number of determinations_____________ 12 SEE a0 ict (6), J 3 ia ae HESEZIESOUN Ls sou!) tee ke hae 8 at 29. 05 28. 39 30. 04 28. 27 27. 50 29. 20 POTS SRS I eg re mT Let RECAPITULATION

vegetable products are exposed to temperatures at or below their actual freezing points. Under certain conditions many of these

! injury, while, on the other hand, some products are injured by chilling | if stored at temperatures well above their actual freezing points.

‘\

8 BULLETIN 1133, U. S. DEPARTMENT OF AGRICULTURE

Evidence seems to show that different individuals of the same variety and strain when grown under different conditions will have somewhat different freezing points, and that there are also some variations in the freezing points of products of the same variety and from the same lot.

In view of these facts the freezing points given in this bulletin should be considered only as danger points at or near which, either above or below, there is a possibility of freezing injury if exposed for a sufficient length of time. These are temperatures at which it is unsafe to hold produce for any length of time, as serious danger of frost injury exists.

Fruits—The average of the freezing points of 9 varieties of sum- mer apples was found to be 28.44° F., while the average for 14 varieties of fall and winter apples was 28.49° ‘and 28.53° for eastern-grown and western-grown fruit, respectively, showing very little difference be- tween the results for apples of the same varieties.

The freezing points of 7 varieties of cherries averaged 27.81° F-.; 7 varieties of American grapes, 28.16°; 2 varieties of European erapes, 24.60°; 6 varieties of oranges, 28.03°; 11 varieties of peaches, 29.41°; 4 varieties of plums, 25.53.05 22 varieties of strawberries, 29.93°; black- berries, 29.15°: white blackberries, 28.40°; Logan blackberries, 29. Es

red raspberries, 30.41°; black raspberries, 28.76°; cranberries 27 16°:

green bananas, peel 29.84°, pulp 30.22°; ripe bananas, peel 29.36°, pulp 26°; currants, 30.21°; gooseberries, 28.91°; grapefruit 28.36°; hard-ripe Bartlett pears, 28.46°; soft-ripe Bartlett pears, 27.83°; Japanese pears (unknown variety), 29.39°; Japanese persimmons (Tanenashi), 28.33°.

Fruits freezing above 30° F. are green bananas (pulp), currants, and red raspberries. Those freezing between 29° and 30° are green _ bananas (peel), ripe bananas (peel), blackberries, Logan blackberries, peaches, Japanese pears, and strawberries. Those freezing between 28° and 29° are apples, blackberries (white), gooseberries, grapes, grapefruit, lemons, oranges, Bartlett pears (hard ripe), Japanese per- simmons (Tanenashi), plums, and raspberries (black). Those freezing between 27° and 28° are cherries and Bartlett pears (soft ripe). Cranberries and ripe bananas (pulp) freeze between 26° and 27° European grapes froze at 24.60°, and Italian chestnuts and Persian or so-called English walnuts froze at 23.80° and 20.00°, respectively.

Vegetables —The average freezing point of 18 varieties of potatoes was 28.92° F.; for 20 varieties of sweet potatoes, 28.44°; and for 19 varieties of tomatoes (ripe), 30.38°. The freezing points of other vegetables investigated were beans (snap), 29. es cabbage, 31.18°; carrots, 29.57° ; cauliflower, 30.08°; celery, DORR ; sweet corn, 28.95°; egeplant, 30. 41° kohl-rabi, 30. 02°: lettuce, 31 .20°; onions (dry), 30.09°; onion sets, 29.50°; peas (green), 30. 03°: turnips, a0-4o5

Two vegetables froze above Sen yin. cabbage and lettuce. Those freezing between 30° and 31° were cauliflower, eggplant, kohl-rabi, onions, peas, tomatoes, and turnips. Those freezing between 29° and 30° were beans, carrots, celery and onion sets. Sweet corn, potatoes, and sweet potatoes froze between 28° and 29°.

Cut flowers.—Determinations of the freezing points of the petals and leaves of Easter lilies, peonies, and roses “show that Easter lily petals freeze between 27° and 28° F.; rose leaves and peony leaves, between 28° and 29°; peony petals and Easter lily leaves, between 29° and 30°; and rosé petals, between 30° and 31°.

U.S. GOVERNMENT PRINTING OFFICE: 1929

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